Prior to spork15 activation on April 2, 2019 deterministic masternode registration required the owner key and voting key be the same. After spork15 activation, the voting key can be updated so that it is different from the owner key.
If you would like to use NODE40 to vote for Dash budget proposals, you will need to update your masternode registration to use the NODE40 voting public key. This public key can be found on the Commissioned Nodes page. To access the Commissioned Nodes page, click on the My Nodes link in the left menu of NODE40 Hosting.
The Commissioned Nodes page will show you if your masternode is registered with the NODE40 voting public key. If you are not using the NODE40 voting public key, you can update your registration from the Dash Core wallet with the following command.
protx update_registrar [proTxHash] [Operator Key] [NODE40 Voting Key] [Payout Address]
The four attributes you need (proTxHash, Operator Key, NODE40 Voting Key, Payout Address) are available from the Commissioned Nodes page.
NOTE: The Dash Mastedernode Tool (DMT) does not yet support the update_registrar command. We will update this support document once the DMT allows for masternode updates. In the meantime, visit our support document on how to use the Dash Core wallet to update your DMT masternodes.